Investigation of free and bound excitons in strained ZnTe films grown by MBE on GaAs(100) substrates

Photoluminescence of ZnTe and ZnTe:Cr grown by molecular-beam epitaxy

“…The first phonon replica of the A 1 peak appears at 2.3431 eV, separated in energy by 26 meV (i.e., the LO-phonon energy) from A 1 , and is indicated by an asterisk. This line has been observed by many groups [3][4][5]7,[9][10][11][12][13] and has been attributed to a column-IV double acceptor 3,4,7 or to lattice defects such as V Zn . This assignment indicates that trace amounts of arsenic from the GaAs substrate have diffused into the II-VI layer and formed As Te acceptors.…”

“…31 The predicted strain shifts in the exciton transition energies for ZnTe at 5 K are shown in Fig. 2,4,7,[9][10][11][12] Note that the small slope of the X hh curve makes it difficult to use the 5-K heavy-hole exciton PL peak to determine the amount of strain present in the epilayer. The hatched region in Fig.…”

“…Its band gap is about 2.25 eV at room temperature and 2.3941 eV at 1.6 K. 1 Many groups have reported photoluminescence (PL) from ZnTe films grown on GaAs. [2][3][4][5]7,[9][10][11][12] There has been some debate about the origin of excitonic bands near 2.375 and 2.379 eV at 5 K. The emission observed near 2.375 eV has been attributed only to the light-hole exciton ͑X lh ͒, 4,7-9,11,12 to a superposition of ͑D 0 , X͒ and ͑D 0 , h͒, 3 or to a superposition of ͑D 0 , X͒ and X lh . [2][3][4][5]7,[9][10][11][12] There has been some debate about the origin of excitonic bands near 2.375 and 2.379 eV at 5 K. The emission observed near 2.375 eV has been attributed only to the light-hole exciton ͑X lh ͒, 4,7-9,11,12 to a superposition of ͑D 0 , X͒ and ͑D 0 , h͒, 3 or to a superposition of ͑D 0 , X͒ and X lh .…”

“…[2][3][4][5][6][7][8][9][10][11][12][13] Because of the mismatches in thermal coefficients and lattice constants between the thin film and substrate, elastic-strain shifts in excitonic emission lines must be considered when making transition assignments. 5,13 The band near 2.379 eV has been assigned to the heavy-hole exciton 4,5,[7][8][9][11][12][13] or to a close superposition of the heavy-hole and light-hole excitons. 5,13 The band near 2.379 eV has been assigned to the heavy-hole exciton 4,5,[7][8][9][11][12][13] or to a close superposition of the heavy-hole and light-hole excitons.…”